1. Technical Field
The invention relates to a fuel injection system for a turbojet. More precisely, it relates to an injection system that comprises a fixed part and a sliding crossmember comprising a flange mounted so as to slide on a sliding surface of the fixed part of the injection system, the fixed part comprising antirotation means and the flange of the sliding crossmember comprising complementary antirotation means which interact with those of the fixed part to limit the rotation of the sliding crossmember relative to the fixed part.
2. Description of the Prior Art
Turbojet combustion chambers comprise an inner wall and an outer wall connected at their upstream ends by an annular base to define an annular combustion chamber base. Injection systems evenly distributed over the periphery of the combustion chamber base deliver a mixture of air and fuel that is burnt to provide combustion gases.
An injection system consists of a fixed part which comprises one, and more generally two swirler elements in which the air is rotated, a Venturi and a bowl. The fixed part also comprises a ring comprising a sliding surface. A sliding crossmember comprising a centering part, usually a cone, is designed to center a fuel injector relative to the longitudinal axis of the swirler.
It is known in the prior art to mount the sliding crossmember, sliding relative to the fixed part of the injection system, in order, on the one hand, to accommodate the relative movements of the chamber and the fuel injector due to differential expansions of the various parts forming the engine and, on the other hand, to take account of the manufacturing tolerances. U.S. Pat. No. 5,117,624 describes a sliding crossmember of this type. Furthermore, it is necessary to provide antirotation means in order to prevent rotation of the sliding crossmember relative to the fixed part of the injection system. Specifically, this rotation, when it may occur, causes rapid wear of the parts and considerably reduces their service life. In the device described in the American patent cited hereinabove, these antirotation means consist of a cup having two parallel walls and of a flange of the sliding crossmember comprising two straight faces parallel to sides of the flange. A relatively large clearance is provided between the flange of the sliding crossmember and the straight faces of the cup in order to make it possible, as previously explained, to accommodate the differential expansions and manufacturing tolerances. Nevertheless, the clearance is sufficiently small to prevent a complete rotation of the sliding crossmember relative to the cup of the injection system. However, an antirotation device of this type is difficult to manufacture. It is therefore relatively costly.